A synergistic catalytic degradation recycling method of ultrahigh molecular weight polyethylene fibers

Abstract

This invention discloses a synergistic catalytic degradation and recycling method for ultra-high molecular weight polyethylene (UHMWPE) fibers, relating to the field of polymer material recycling technology. The method includes: shearing, ultrasonically cleaning, and drying UHMWPE fibers to obtain pretreated fibers; dissolving a bis(acetylacetone)manganese(III) complex in a mixed solvent containing tert-butyl hydrogen peroxide and glacial acetic acid to prepare a chemical catalyst solution; adding the pretreated fibers to the solution for gentle heating and shaking treatment, followed by rinsing and drying to obtain pre-activated fibers; dispersing alkane hydroxylase AlkB in phosphate buffer, adding cofactors NADH and ferrous ammonium sulfate to prepare a biocatalyst suspension; adding the pre-activated fibers to the suspension for isothermal shaking culture for biocatalytic degradation; and obtaining oligomer / small molecule platform compounds through solid-liquid separation, concentration, alcohol precipitation, centrifugation, and drying. This invention achieves high-value-added recycling by efficiently degrading UHMWPE fibers under mild conditions through the synergistic effect of chemical and biocatalysis.

Description

Technical Field

[0001] This invention relates to the field of polymer material recycling technology, specifically to a synergistic catalytic degradation and recycling method for ultra-high molecular weight polyethylene fiber. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber is widely used in high-end fields such as bulletproof protection, marine ropes, medical devices, and sports equipment due to its excellent specific strength, specific modulus, chemical corrosion resistance, and impact resistance. However, the ultra-high molecular weight and high crystallinity of UHMWPE endow it with extremely strong chemical inertness and biological resistance, making its waste almost impossible to degrade in the natural environment, causing serious environmental pollution and resource waste. Existing UHMWPE recycling technologies mainly include mechanical recycling, pyrolysis, and solvent dissolution. Although mechanical recycling is simple to operate, the molecular weight and mechanical properties of the recycled products are significantly reduced, limiting its use to low-value-added products. Pyrolysis requires high-temperature conditions of 350–500℃, resulting in high energy consumption, complex product composition, and difficulty in precise control. While solvent dissolution can recover high-quality UHMWPE, it requires the use of large amounts of organic solvents (such as decahydronaphthalene and xylene), leading to problems such as high solvent toxicity, difficult recycling, and poor economic efficiency.

[0003] In recent years, research on the degradation of polyolefin materials using bio-enzymes has attracted widespread attention. However, due to the high crystallinity and dense molecular chain stacking structure of UHMWPE, the degradation efficiency of single bio-enzymes is extremely low, posing a significant challenge to practical applications. Therefore, there is an urgent need to develop a mild, green, and efficient method for the degradation and recycling of UHMWPE fibers to achieve the sustainable recycling of this type of high-performance fiber. Summary of the Invention

[0004] The purpose of this invention is to provide a synergistic catalytic degradation and recycling method for ultra-high molecular weight polyethylene fibers, so as to solve the technical problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fibers includes the following steps: (1) The UHMWPE fiber was cut into short fibers, and then pretreated fibers were obtained by ultrasonic cleaning, rinsing and drying with nonionic surfactant; (2) Dissolve the bis(acetylacetone)manganese(III) complex in a mixed solvent containing tert-butyl hydrogen peroxide and glacial acetic acid to prepare a chemical catalyst solution; (3) The pretreated fiber is added to the chemical catalyst solution and subjected to constant temperature shaking under mild heating conditions. After rinsing and drying, the preactivated fiber is obtained. (4) Disperse alkane hydroxylase AlkB in phosphate buffer, add cofactor NADH and auxiliary electron transporter ferrous ammonium sulfate, and prepare a biocatalyst suspension; (5) Add the pre-activated fiber to the biocatalyst suspension and carry out biocatalytic degradation treatment by shaking culture under constant temperature conditions; (6) The degradation mixture was filtered, concentrated by vacuum distillation, precipitated with alcohol, separated by centrifugation, and dried to obtain oligomer / small molecule platform compound products.

[0006] In the technical solution of this invention, the efficient degradation of ultra-high molecular weight polyethylene fiber is achieved from the following aspects: (1) Under mild heating conditions, a low concentration of bis(acetylacetone)manganese(III) complex chemical catalyst is used to pre-activate UHMWPE fiber. In the bis(acetylacetone)manganese(III) complex, manganese(III) ions have a moderate redox potential. Under the synergistic effect of tert-butyl hydrogen peroxide, highly active manganese-oxygen free radical intermediates can be generated in situ through a Fenton-like reaction mechanism. This active oxygen species can selectively attack the low-energy tertiary carbon CH bonds and C / C bonds at the branch nodes in the long-chain molecules of UHMWPE, introducing oxygen-containing functional groups (such as hydroxyl, carbonyl and carboxyl groups) at these weak sites, thereby destroying the regular arrangement and close packing of molecular chains in the fiber crystal region without causing large-scale molecular chain breakage. Acetic acid plays a dual role in the system: on the one hand, it acts as a weak acid buffer medium to maintain the pH of the system in the range of 3 to 5, ensuring the catalytic activity and structural stability of the manganese complex; on the other hand, acetic acid molecules can penetrate into the amorphous region of UHMWPE fiber, further promoting the swelling and relaxation of molecular chains. After pre-activation treatment, the crystallinity of UHMWPE fiber decreased from the original 70% to 80% to 40% to 55%, the density of oxygen-containing functional groups on the surface increased significantly, and the micromorphology of the fiber surface changed from smooth and dense to rough and porous. These changes created a large number of attackable active sites and diffusion channels for subsequent biocatalytic degradation. (2) The alkane hydroxylase AlkB was introduced to biocatalytically degrade the pre-activated UHMWPE fiber. AlkB enzyme belongs to the non-heme diferric oxygenase family. Its active center contains a diferric core structure and can use the electrons provided by NADH to activate molecular oxygen into high-valence iron-oxygen active species. This species has a very strong CH bond activation ability. Based on the pre-activation treatment that introduces oxygen-containing functional groups and micropores into the fiber, AlkB enzyme molecules can anchor to active sites on the fiber surface through their hydrophobic substrate binding channels. Using the hydroxyl and carbonyl groups introduced in the pre-activation stage as guiding markers, they recognize and attack adjacent C-C backbone bonds, gradually cleaving the UHMWPE long chain into carbon chain lengths of C8-C through an oxidative cleavage mechanism. 20The enzyme consists of oligomers and small fatty acid molecules. The substrate specificity of AlkB enzymes ensures high selectivity at the cleavage sites, avoiding the problem of disordered cleavage and the resulting complex mixtures found in pyrolysis. Ferrous ammonium sulfate, acting as an auxiliary electron transporter, maintains the redox cycle of the AlkB enzyme's diferric active center, ensuring the enzyme's structural integrity and catalytic efficiency during long-term catalysis. The synergistic effect of the two-stage catalysis lies in the fact that the directionally introduced oxygen-containing functional groups and microporous structures in the chemocatalytic stage not only increase the effective surface area accessible to enzyme molecules, but also weaken the bond energy of adjacent C / C bonds due to the polar effect of the oxygen-containing groups, thus significantly increasing the catalytic cleavage rate of AlkB enzymes.

[0007] Preferably, in step (1), the short fiber length is 3-10 mm, the mass fraction of the nonionic surfactant aqueous solution is 1%-3%, the ultrasonic cleaning temperature is 40-50℃, and the cleaning time is 15-30 min.

[0008] Preferably, in step (2), the mass ratio of tert-butyl hydroperoxide to glacial acetic acid is (4-6):10.

[0009] Preferably, in step (3), the solid-liquid ratio of the pretreated fiber to the chemical catalyst solution is 5:60 to 5:80 (g / mL), the treatment temperature is 55 to 70°C, the treatment time is 4 to 8 hours, and the oscillation rate is 120 to 180 rpm.

[0010] Preferably, in step (4), the mass ratio of alkane hydroxylase AlkB, cofactor NADH, and auxiliary electron transporter ferrous ammonium sulfate is 3:(0.5-0.8):(0.1-0.2).

[0011] In the actual research and development process, the research team found that although the oxygen-containing functional groups introduced in the chemical catalytic pre-activation stage effectively reduced the crystallinity of the fiber and created active sites, they also brought about a tricky technical problem: intermediate oxidation products such as aldehyde groups and peroxy groups generated during the pre-activation process were locally enriched on the fiber surface. These active oxide species produced an oxidative poisoning effect on the iron-sulfur clusters at the active center of AlkB enzyme, causing the enzyme activity to rapidly decrease by about 40% to 60% in the early stage of degradation (first 6 to 8 hours), which seriously restricted the efficiency of subsequent biocatalytic degradation. In order to solve this technical problem, the present invention adopts the following method: (1) After the chemical catalytic pre-activation treatment in step three is completed, a strict deionized water rinsing procedure (rinsing 5 times) is added, and the residual peroxide content is detected in the rinsing solution (using the potassium iodide-starch test paper method for rapid qualitative detection) to ensure that the free peroxides and residual manganese catalyst on the surface of the pre-activated fiber are fully removed. Meanwhile, the vacuum drying step at 40-50℃ not only removes moisture, but also uses mild heating conditions to decompose the unstable peroxide intermediates adsorbed on the fiber surface into stable hydroxyl and carbonyl groups, eliminating the toxic factors to the enzyme from the source; (2) Ferrous ammonium sulfate is added to the biocatalyst suspension in step four as an auxiliary electron transporter. Ferrous ammonium sulfate plays multiple protective functions in the system: the Fe it provides 2+ Ions, acting as sacrificial reducing agents, preferentially react with trace amounts of oxidizing species that may remain on the fiber surface, effectively constructing a chemical protective barrier around the enzyme molecules, protecting the double-iron active site of the AlkB enzyme from oxidative damage; simultaneously, Fe... 2+ It participates in the electron transport chain cycle within the AlkB enzyme, maintaining the continuous operation of the catalytic cycle. The synergistic effect of these two measures, from the dimensions of removing chemical residues and protecting the enzyme active site, effectively solves the compatibility problem between the two-stage catalysis, increasing the enzyme activity retention rate in the biocatalytic stage from the initial 40% to over 85%, achieving a true complementary advantage between chemical catalysis and biocatalysis.

[0012] Preferably, in step (5), the solid-liquid ratio of the pre-activated fiber to the biocatalyst suspension is 1:40 to 2:40 (g / mL), the degradation temperature is 30 to 37°C, the degradation time is 24 to 72 h, and the oscillation rate is 100 to 150 rpm.

[0013] Preferably, in step (6), the vacuum distillation temperature is 45-55°C, and anhydrous ethanol is used for alcohol precipitation, with precipitation allowed to stand at 4°C for 6-12 hours.

[0014] Preferably, in step (6), the centrifugation speed is 8000-10000 rpm, the centrifugation time is 15-20 min, and the drying conditions are vacuum drying at 40-50℃ to constant weight.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) Chemical catalytic pre-activation selectively reduces fiber crystallinity and introduces a large number of active sites, thereby increasing the biocatalytic degradation efficiency by 3 to 5 times; (2) Biocatalytic degradation has high specificity and the product composition is controllable, avoiding the problem of complex products in pyrolysis. (3) The entire process is carried out under mild conditions, with low energy consumption, which is significantly better than the traditional pyrolysis method; (4) The catalyst dosage is low, the reagents used are environmentally friendly, and the method is green and sustainable; (5) The degradation products are oligomers and small molecule platform compounds with industrial application value, and the resource utilization rate is high. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1 A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fibers includes the following steps: Step 1: Take UHMWPE fibers with a viscosity-average molecular weight of 3 million g / mol and a crystallinity of approximately 75%, and cut them into short fibers with a length of approximately 8 mm. Weigh 10 g of the short fibers and add them to 200 mL of a 2.5% (w / w) nonylphenol polyoxyethylene ether (OP-10) aqueous solution. Clean the fibers using ultrasonic cleaning at 43°C and an ultrasonic frequency of 40 kHz for 25 min. After cleaning, rinse the fibers four times with deionized water and dry them in a vacuum drying oven at 55°C for 5 h for later use.

[0018] Step 2: Weigh 0.0352 g of the bis(acetylacetone)manganese(III) complex and dissolve it in a mixed solvent consisting of 5.5 g tert-butyl hydroperoxide, 10.0 g 10% glacial acetic acid, and 85.0 g deionized water. Stir magnetically at 40°C for 25 min to completely dissolve the catalyst. The solution should be light brown and transparent. Prepare and use immediately.

[0019] Step 3: Add 5g of the short fibers treated in Step 1 to 70mL of the chemical catalyst solution obtained in Step 2, transfer to a 500mL Erlenmeyer flask, and treat with shaking in a constant temperature shaking incubator at 65℃ for 7h at a shaking rate of 150rpm. After treatment, remove the fibers, rinse 5 times with deionized water, and test the final rinse solution with potassium iodide-starch paper. If no color develops, it confirms that the residual peroxide has been completely removed. Vacuum dry at 45℃ for 2.5h to obtain pre-activated fibers.

[0020] Step 4: Disperse 0.3g of lyophilized alkane hydroxylase AlkB in 300mL of phosphate buffer (75mmol / L, pH 7.2). Add 0.0638g of NADH and 0.0118g of ferrous ammonium sulfate. Gently stir at 35°C for 12min to fully disperse and activate the enzyme. Prepare and use immediately.

[0021] Step 5: Add the pre-activated fiber obtained in Step 3 to the biocatalyst suspension obtained in Step 4 at a mass-to-volume ratio of 1.8 g / 40 mL. Incubate in a constant-temperature shaking incubator at 35℃ and pH=7.2 for 60 h with shaking at a shaking rate of 120 rpm. Supplement with 0.032 g of NADH every 12 h during the incubation process, for a total of 3 times.

[0022] Step 6: Filter the degradation mixture from Step 5 through a 200-mesh stainless steel filter, collecting approximately 280 mL of filtrate (after deducting sampling losses). Concentrate the filtrate to approximately 70 mL (about 1 / 4 of the original volume) by vacuum distillation in a rotary evaporator at 50°C and a vacuum of -0.09 MPa. Add 175 mL of anhydrous ethanol (2.5 times the volume) to the concentrate, mix thoroughly, and allow to settle at 4°C for 10 h. Centrifuge at 9000 rpm for 18 min, collect the precipitate, and wash twice with 20 mL of anhydrous ethanol. Dry to constant weight in a vacuum drying oven at 43°C to obtain the degradation product.

[0023] Example 2 A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fibers includes the following steps: Step 1: Take UHMWPE fibers with a viscosity-average molecular weight of 3 million g / mol and a crystallinity of approximately 75%, and cut them into short fibers with a length of approximately 4 mm. Weigh 10 g of the short fibers and add them to 200 mL of a 1.5% (w / w) nonylphenol polyoxyethylene ether (OP-10) aqueous solution. Clean the fibers using ultrasonic cleaning at 43°C and an ultrasonic frequency of 40 kHz for 18 min. After cleaning, rinse the fibers four times with deionized water and dry them in a vacuum drying oven at 55°C for 5 h for later use.

[0024] Step 2: Weigh 0.0352 g of the bis(acetylacetone)manganese(III) complex and dissolve it in a mixed solvent consisting of 4.5 g tert-butyl hydroperoxide, 10.0 g 10% glacial acetic acid, and 85.0 g deionized water. Stir magnetically at 40 °C for 25 min to completely dissolve the catalyst. The solution should be light brown and transparent. Prepare and use immediately.

[0025] Step 3: Add 5g of the short fibers treated in Step 1 to 70mL of the chemical catalyst solution obtained in Step 2, transfer to a 500mL Erlenmeyer flask, and incubate at 60℃ with shaking for 5h at a shaking rate of 130rpm. After treatment, remove the fibers, rinse 5 times with deionized water, and test the final rinse solution with potassium iodide-starch paper. If no color develops (confirming complete removal of residual peroxides), vacuum dry at 45℃ for 2.5h to obtain pre-activated fibers.

[0026] Step 4: Disperse 0.3g of lyophilized alkane hydroxylase AlkB in 300mL of phosphate buffer (75mmol / L, pH 7.2). Add 0.0638g of NADH and 0.0118g of ferrous ammonium sulfate. Gently stir at 35°C for 12min to fully disperse and activate the enzyme. Prepare and use immediately.

[0027] Step 5: Add the pre-activated fiber obtained in Step 3 to the biocatalyst suspension obtained in Step 4 at a mass-to-volume ratio of 1.2 g / 40 mL. Incubate in a constant-temperature shaking incubator at 35℃ and pH=7.2 for 35 h with shaking at a shaking rate of 120 rpm. Supplement with 0.032 g of NADH every 12 h during the incubation process, for a total of 3 times.

[0028] Step 6: Filter the degradation mixture from Step 5 through a 200-mesh stainless steel filter, collecting approximately 280 mL of filtrate (after deducting sampling losses). Concentrate the filtrate to approximately 70 mL (about 1 / 4 of the original volume) by vacuum distillation in a rotary evaporator at 50°C and a vacuum of -0.09 MPa. Add 175 mL of anhydrous ethanol (2.5 times the volume) to the concentrate, mix thoroughly, and allow to settle at 4°C for 8 hours. Centrifuge at 9000 rpm for 18 minutes, collect the precipitate, and wash twice with 20 mL of anhydrous ethanol. Dry to constant weight in a vacuum drying oven at 43°C to obtain the degradation product.

[0029] Example 3 A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fibers includes the following steps: Step 1: Take UHMWPE fibers with a viscosity-average molecular weight of 3 million g / mol and a crystallinity of approximately 75%, and cut them into short fibers with a length of approximately 6 mm. Weigh 10 g of the short fibers and add them to 200 mL of a 2% (w / w) nonylphenol polyoxyethylene ether (OP-10) aqueous solution. Clean the fibers using ultrasonic cleaning at 43°C and an ultrasonic frequency of 40 kHz for 20 min. After cleaning, rinse the fibers four times with deionized water and dry them in a vacuum drying oven at 55°C for 5 h for later use.

[0030] Step 2: Weigh 0.0352 g of the bis(acetylacetone)manganese(III) complex and dissolve it in a mixed solvent consisting of 5.0 g tert-butyl hydroperoxide, 10.0 g 10% glacial acetic acid, and 85.0 g deionized water. Stir magnetically at 40°C for 25 min to completely dissolve the catalyst. The solution should be light brown and transparent. Prepare and use immediately.

[0031] Step 3: Add 5g of the short fibers treated in Step 1 to 70mL of the chemical catalyst solution obtained in Step 2, transfer to a 500mL Erlenmeyer flask, and incubate at 60℃ with shaking for 6h at a shaking rate of 150rpm. After treatment, remove the fibers, rinse 5 times with deionized water, and test the final rinse solution with potassium iodide-starch paper. If no color develops (confirming complete removal of residual peroxides), vacuum dry at 45℃ for 2.5h to obtain pre-activated fibers.

[0032] Step 4: Disperse 0.3g of lyophilized alkane hydroxylase AlkB in 300mL of phosphate buffer (75mmol / L, pH 7.2). Add 0.0638g of NADH and 0.0118g of ferrous ammonium sulfate. Gently stir at 35°C for 12min to fully disperse and activate the enzyme. Prepare and use immediately.

[0033] Step 5: Add the pre-activated fiber obtained in Step 3 to the biocatalyst suspension obtained in Step 4 at a mass-to-volume ratio of 1.5 g / 40 mL. Incubate in a constant-temperature shaking incubator at 35℃ and pH=7.2 for 50 h with shaking at a shaking rate of 120 rpm. Supplement with 0.032 g of NADH every 12 h during the incubation process, for a total of 3 times.

[0034] Step 6: Filter the degradation mixture from Step 5 through a 200-mesh stainless steel filter, collecting approximately 280 mL of filtrate (after deducting sampling losses). Concentrate the filtrate to approximately 70 mL (about 1 / 4 of the original volume) by vacuum distillation in a rotary evaporator at 50°C and a vacuum of -0.09 MPa. Add 175 mL of anhydrous ethanol (2.5 times the volume) to the concentrate, mix thoroughly, and allow to settle at 4°C for 8 hours. Centrifuge at 9000 rpm for 18 minutes, collect the precipitate, and wash twice with 20 mL of anhydrous ethanol. Dry to constant weight in a vacuum drying oven at 45°C to obtain the degradation product.

[0035] Example 4 A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fibers includes the following steps: Step 1: Take UHMWPE fibers with a viscosity-average molecular weight of 3 million g / mol and a crystallinity of approximately 75%, and cut them into short fibers with a length of approximately 10 mm. Weigh 10 g of the short fibers and add them to 200 mL of a 3% (w / w) nonylphenol polyoxyethylene ether (OP-10) aqueous solution. Clean the fibers using ultrasonic cleaning at 50°C and an ultrasonic frequency of 40 kHz for 30 min. After cleaning, rinse the fibers four times with deionized water and dry them in a vacuum drying oven at 55°C for 5 h for later use.

[0036] Step 2: Weigh 0.0352 g of the bis(acetylacetone)manganese(III) complex and dissolve it in a mixed solvent consisting of 6.0 g tert-butyl hydroperoxide, 10.0 g 10% glacial acetic acid, and 85.0 g deionized water. Stir magnetically at 40°C for 25 min to completely dissolve the catalyst. The solution should be light brown and transparent. Prepare and use immediately.

[0037] Step 3: Add 5g of the short fibers treated in Step 1 to 80mL of the chemical catalyst solution obtained in Step 2, transfer to a 500mL Erlenmeyer flask, and treat with shaking in a constant temperature shaking incubator at 70℃ for 8h at a shaking rate of 180rpm. After treatment, remove the fibers, rinse 5 times with deionized water, and test the final rinse solution with potassium iodide-starch paper. If no color develops, it confirms that the residual peroxide has been completely removed. Vacuum dry at 45℃ for 2.5h to obtain pre-activated fibers.

[0038] Step 4: Disperse 0.3g of lyophilized alkane hydroxylase AlkB in 300mL of phosphate buffer (75mmol / L, pH 7.2). Add 0.0638g of NADH and 0.0118g of ferrous ammonium sulfate. Gently stir at 35°C for 12min to fully disperse and activate the enzyme. Prepare and use immediately.

[0039] Step 5: Add the pre-activated fiber obtained in Step 3 to the biocatalyst suspension obtained in Step 4 at a mass-to-volume ratio of 2 g / 40 mL. Incubate in a constant-temperature shaking incubator at 37℃ and pH=7.2 for 72 h with shaking at a shaking rate of 150 rpm. Supplement with 0.032 g of NADH every 12 h during the incubation process, for a total of 3 times.

[0040] Step 6: Filter the degradation mixture from Step 5 through a 200-mesh stainless steel filter, collecting approximately 280 mL of filtrate (after deducting sampling losses). Concentrate the filtrate to approximately 70 mL (about 1 / 4 of the original volume) by vacuum distillation in a rotary evaporator at 55°C and a vacuum of -0.09 MPa. Add 175 mL of anhydrous ethanol (2.5 times the volume) to the concentrate, mix thoroughly, and allow to settle at 4°C for 12 h. Centrifuge at 10000 rpm for 20 min, collect the precipitate, and wash twice with 20 mL of anhydrous ethanol. Dry to constant weight in a vacuum drying oven at 50°C to obtain the degradation product.

[0041] Example 5 A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fibers includes the following steps: Step 1: Take UHMWPE fibers with a viscosity-average molecular weight of 3 million g / mol and a crystallinity of approximately 75%, and cut them into short fibers with a length of approximately 3 mm. Weigh 10 g of the short fibers and add them to 200 mL of a 1% (w / w) aqueous solution of nonylphenol polyoxyethylene ether (OP-10). Clean the fibers using ultrasonic cleaning at 40°C and an ultrasonic frequency of 40 kHz for 15 min. After cleaning, rinse the fibers four times with deionized water and dry them in a vacuum drying oven at 55°C for 5 h for later use.

[0042] Step 2: Weigh 0.0352 g of the bis(acetylacetone)manganese(III) complex and dissolve it in a mixed solvent consisting of 4.0 g tert-butyl hydroperoxide, 10.0 g 10% glacial acetic acid, and 85.0 g deionized water. Stir magnetically at 40°C for 25 min to completely dissolve the catalyst. The solution should be light brown and transparent. Prepare and use immediately.

[0043] Step 3: Add 5g of the short fibers treated in Step 1 to 60mL of the chemical catalyst solution obtained in Step 2, transfer to a 500mL Erlenmeyer flask, and incubate at 55℃ with shaking for 4h at a shaking rate of 120rpm. After treatment, remove the fibers, rinse 5 times with deionized water, and test the final rinse solution with potassium iodide-starch paper. If no color develops (confirming complete removal of residual peroxides), vacuum dry at 45℃ for 2.5h to obtain pre-activated fibers.

[0044] Step 4: Disperse 0.3g of lyophilized alkane hydroxylase AlkB in 300mL of phosphate buffer (75mmol / L, pH 7.2). Add 0.0638g of NADH and 0.0118g of ferrous ammonium sulfate. Gently stir at 35°C for 12min to fully disperse and activate the enzyme. Prepare and use immediately.

[0045] Step 5: Add the pre-activated fiber obtained in Step 3 to the biocatalyst suspension obtained in Step 4 at a mass-to-volume ratio of 1 g / 40 mL. Incubate in a constant-temperature shaking incubator at 30℃ and pH=7.2 for 24 h with shaking at a shaking rate of 100 rpm. Supplement with 0.032 g of NADH every 12 h during the incubation process, for a total of 3 times.

[0046] Step 6: Filter the degradation mixture from Step 5 through a 200-mesh stainless steel filter, collecting approximately 280 mL of filtrate (after deducting sampling losses). Concentrate the filtrate to approximately 70 mL (about 1 / 4 of the original volume) by vacuum distillation in a rotary evaporator at 45°C and a vacuum of -0.09 MPa. Add 175 mL of anhydrous ethanol (2.5 times the volume) to the concentrate, mix thoroughly, and allow to settle at 4°C for 6 hours. Centrifuge at 8000 rpm for 15 minutes, collect the precipitate, and wash twice with 20 mL of anhydrous ethanol. Dry to constant weight in a vacuum drying oven at 40°C to obtain the degradation product.

[0047] Comparative Example 1: Basically the same as Example 1, but steps 2 and 3 are omitted, that is, the UHMWPE fibers are not chemically catalytically pre-activated, and the pre-treated fibers are directly added to the biocatalyst suspension for degradation. The remaining steps and parameters are exactly the same as in Example 1.

[0048] Comparative Example 2: Basically the same as Example 1, but steps 4 and 5 are omitted, that is, no biocatalytic degradation treatment is performed, and only the product separation and recovery of the chemically catalytically pre-activated fiber is performed. The remaining steps and parameters are exactly the same as in Example 1.

[0049] Comparative Example 3: Basically the same as Example 1, except that ferrous ammonium sulfate was not added as an auxiliary electron transporter in step four. The remaining steps and parameters were exactly the same as in Example 1.

[0050] Performance testing: (1) Degradation rate test: The mixture after biocatalytic degradation was vacuum filtered through a 200-mesh stainless steel filter screen. The residual solids on the filter screen were collected and rinsed three times with deionized water to remove soluble degradation products adhering to the surface. Then, it was dried to constant weight in a vacuum drying oven at 50℃, and the mass of the residual solids was accurately weighed using an analytical balance. The degradation rate was calculated using the formula: Degradation rate (%) = (m0-m1) / m0 × 100%, where m0 is the mass of the pre-activated fiber before the biocatalytic degradation step (the mass of the pre-treated fiber in Comparative Example 1), and m1 is the dry weight of the residual solids after degradation treatment. Each group of samples was tested in parallel three times, and the average value was taken.

[0051] (2) Pre-activated fiber crystallinity test: Differential scanning calorimetry (DSC) was used to determine the crystallinity of the fibers after chemical catalytic pre-activation treatment. 5–8 mg of pre-activated fiber sample was placed in an aluminum sealed crucible and heated from 30 °C to 200 °C at a rate of 10 °C / min under a nitrogen protective atmosphere (flow rate 50 mL / min). The temperature curve was recorded. The enthalpy of complete crystallization of UHMWPE was used as the enthalpy of fusion. Based on this, crystallinity is calculated using the formula: Xc(%) = ΔH m / ΔH0×100%, where ΔH m The measured enthalpy of fusion is given for the sample. A TA Q2000 differential scanning calorimeter was used, with a temperature accuracy of ±0.1℃. Comparative Example 1 underwent no chemical catalytic pre-activation; its crystallinity was the same as that of the original UHMWPE fiber (approximately 75%).

[0052] (3) Oxygen index test of pre-activated fiber surface: X-ray photoelectron spectroscopy (XPS) was used to characterize the degree of introduction of oxygen-containing functional groups on the fiber surface after chemical catalytic pre-activation treatment. The pre-activated fiber sample was cut into a flat film of 5 mm × 5 mm, fixed on the XPS sample stage, and excited by Al Kα rays (hv = 1486.6 eV) under ultra-high vacuum conditions (vacuum degree < 5 × 10⁻⁶). -8 The full spectrum and narrow-region fine scanning of C1s and O1s regions were performed using a Thermo Scientific K-Alpha XPS instrument. The surface oxygen-to-carbon atomic ratio (O / C) was calculated by the ratio of the O1s to C1s peak areas, which served as a quantitative indicator of the degree of introduction of oxygen-containing functional groups.

[0053] (4) Number-average molecular weight determination of degradation products: The number-average molecular weight of degradation products was determined by gel permeation chromatography (GPC). Approximately 5 mg of the dried degradation product was dissolved in 2 mL of tetrahydrofuran (THF, chromatographic grade), filtered through a 0.22 μm organic phase filter membrane, and injected into the GPC system. Chromatographic conditions: THF was used as the mobile phase, the flow rate was 1.0 mL / min, the column temperature was 35 °C, and a Styragel HR 0.5 + HR 1 + HR 2 tandem column combination (molecular weight detection range 100–20000 g / mol) was used for detection with a differential refractive index detector. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the degradation products were calculated using a narrow-distribution polystyrene standard.

[0054] (5) Degradation product yield test: The oligomer / small molecule platform compound product obtained in step 6 and dried to constant weight was accurately weighed using a 0.01 g analytical balance. The degradation product yield was calculated using the formula: Yield (%) = m2 / m0 × 100%, where The mass of the finally collected dried degradation products is given, and m0 is the mass of the pre-activated fibers before being added to the degradation system (in Comparative Example 1, it is the mass of the pretreated fibers). This indicator reflects the actual degree to which recyclable and effective degradation products are obtained.

[0055] (6) C8-C in the degradation products 20 Component composition analysis: The carbon chain distribution of the degradation products was analyzed using gas chromatography-mass spectrometry (GC-MS). Approximately 2 mg of dried degradation product was dissolved in 1 mL of dichloromethane, filtered through a 0.22 μm organic phase filter membrane, and then injected into the GC-MS system. Chromatographic conditions: HP-5MS capillary column (30 m × 0.25 mm × 0.25 μm), high-purity helium as carrier gas (flow rate 1.2 mL / min), injection port temperature 280 °C; temperature program: initial temperature 50 °C held for 2 min, then increased to 300 °C at 10 °C / min and held for 5 min. Mass spectrometry conditions: EI ion source, electron energy 70 eV, scan range m / z 35–550. Each component was identified by searching the NIST mass spectrometry database, and C8-C was calculated using the peak area normalization method. 20 The total percentage of each component within the carbon chain length range.

[0056] (7) Enzyme activity retention rate test: After the biocatalytic degradation treatment, 1 mL of the supernatant of the degradation mixture was taken, and the residual catalytic activity of AlkB enzyme was determined by spectrophotometry. Using octane as a model substrate, in a standard reaction system (containing 0.3 mmol / L NADH, 0.1 mmol / L ferrous ammonium sulfate, 75 mmol / L PBS buffer pH=7.2, and 0.5 mmol / L octane emulsion), the reaction was carried out at 35℃ for 10 min, and the enzyme catalytic reaction rate was calculated by the rate of decrease of NADH absorbance at 340 nm. The enzyme activity retention rate was calculated by the formula: enzyme activity retention rate (%) = V1 / V0 × 100%, where V1 is the residual enzyme catalytic reaction rate after degradation, and V0 is the initial catalytic reaction rate of the enzyme in the same volume of supernatant before degradation. Comparative Example 2 does not involve the biocatalytic degradation step, so this item was not tested.

[0057] The test results for each embodiment and comparative example are shown in the table below:

[0058] It can be seen from the above table: (1) Comparing Examples 1-5 with Comparative Example 1, it can be seen that chemical catalytic pre-activation treatment is a key prerequisite for achieving efficient biodegradation. In Comparative Example 1, the unactivated UHMWPE fibers maintained their original high crystallinity (75.0%) and extremely low surface oxygen index (O / C only 0.008), making it difficult for enzyme molecules to anchor on the dense and smooth fiber surface. The degradation rate was only 8.2%, and the product's number-average molecular weight was as high as 1850 g / mol, C8-C 20 The target component accounted for only 25.3%, and the product yield was only 2.1%. However, in the embodiments that underwent chemical catalytic preactivation, the fiber crystallinity decreased to 43.2%–54.6%, the surface oxygen index O / C increased to 0.085–0.148, and the degradation rate reached 45.6%–67.3%, an increase of approximately 5.6–8.2 times. This fully demonstrates the decisive role of chemical catalytic preactivation in reducing crystallinity and introducing oxygen-containing active sites.

[0059] (2) Comparing Example 1 and Comparative Example 2, it can be seen that, relying solely on chemical catalytic pre-activation without biocatalytic degradation, although the fiber crystallinity and surface oxygen index are the same as in Example 1 (crystallinity 46.8%, O / C 0.132), the degradation rate is only 14.8%, and the product number-average molecular weight is as high as 4500 g / mol, C8-C 20 The component proportion was only 16.2%, and the product yield was only 5.3%. In contrast, after introducing AlkB enzyme biocatalysis in Example 1, the degradation rate increased significantly from 14.8% to 63.5%, and the number-average molecular weight of the product decreased sharply from 4500 g / mol to 228 g / mol, C8-C 20 The component content increased from 16.2% to 83.6%, and the product yield increased from 5.3% to 29.2%. This comparison strongly validates the irreplaceable role of biocatalysis in achieving deep and specific chain breakage. Chemical catalysis can only achieve shallow oxidation and limited chain breakage, while the specific CH bond activation and C / C bond breaking ability of AlkB enzyme is the core driving force for the efficient conversion of UHMWPE into small molecule compounds.

[0060] (3) Comparing Example 1 and Comparative Example 3, it can be seen that the addition of ferrous ammonium sulfate, an auxiliary electron transporter, is crucial for maintaining the long-term catalytic activity of the enzyme. In Comparative Example 3, without ferrous ammonium sulfate, the enzyme activity retention rate was only 51.8% (due to the poisoning effect of trace oxidizing species remaining on the surface of the pre-activated fiber on the enzyme active site), resulting in a decrease in degradation rate from 63.5% to 38.5%, a decrease of 39.4%; product yield decreased from 29.2% to 16.2%, a decrease of 44.5%; and the number-average molecular weight of the product increased from 228 g / mol to 385 g / mol, C8-C 20The decrease in component proportion from 83.6% to 68.5% indicates that the decline in enzyme activity directly affects the degree of molecular chain breakage. However, after adding ferrous ammonium sulfate (Example 1), the enzyme activity retention rate increased to 86.8%, Fe 2+ Ions, acting as sacrificial reducing agents, effectively neutralize residual oxidative species on the fiber surface, while also participating in the internal electron transport chain cycle of the enzyme, thus fully ensuring the continuous and efficient catalytic capacity of AlkB enzyme.

[0061] (4) Comparing the differences between Examples 1-5, it can be seen that Example 4 performed best in all test indicators (degradation rate 67.3%, product number average molecular weight 198 g / mol, product yield 32.1%, C8-C 20 The component content was 86.2%, which is closely related to the use of a higher pre-activation temperature (70℃), a longer pre-activation time (8h), a higher TBHP dosage, and the longest biodegradation time (72h). Example 5, due to the use of the mildest pre-activation conditions (55℃ / 4h) and the shortest biodegradation time (24h / 30℃), had the lowest relative indicators (degradation rate 45.6%, product yield 18.7%), but was still far superior to the comparative examples, indicating that the synergistic catalytic strategy of the present invention has significant technical effects within a wide process parameter window.

[0062] (5) All five sets of examples achieved a degradation rate of 45% to 67% under mild conditions of 30 to 70°C. The number average molecular weight of the degradation products was less than 325 g / mol, the proportion of C8-C20 target components was more than 71%, and the enzyme activity retention rate was more than 83%. The resulting oligomers and fatty acid small molecule platform compounds have high industrial application value (can be used to prepare lubricant base oil, surfactant precursors, etc.). This shows that the chemical catalytic pre-activation + biocatalytic deep degradation dual-stage synergistic method of the present invention effectively solves the technical problem of difficult degradation of ultra-high molecular weight polyethylene fiber and realizes the complementary advantages of the two catalytic modes.

[0063] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the essence and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber, characterized in that, Includes the following steps: (1) The UHMWPE fiber was cut into short fibers, and then pretreated fibers were obtained by ultrasonic cleaning, rinsing and drying with nonionic surfactant; (2) Dissolve the bis(acetylacetone)manganese(III) complex in a mixed solvent containing tert-butyl hydrogen peroxide and glacial acetic acid to prepare a chemical catalyst solution; (3) The pretreated fiber is added to the chemical catalyst solution and subjected to constant temperature shaking under mild heating conditions. After rinsing and drying, the preactivated fiber is obtained. (4) Disperse alkane hydroxylase AlkB in phosphate buffer, add cofactor NADH and auxiliary electron transporter ferrous ammonium sulfate, and prepare a biocatalyst suspension; (5) Add the pre-activated fiber to the biocatalyst suspension and carry out biocatalytic degradation treatment by shaking culture under constant temperature conditions; (6) The degradation mixture was filtered, concentrated by vacuum distillation, precipitated with alcohol, separated by centrifugation, and dried to obtain oligomer / small molecule platform compound products.

2. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (1), the short fiber length is 3-10 mm, the mass fraction of the nonionic surfactant aqueous solution is 1%-3%, the ultrasonic cleaning temperature is 40-50℃, and the cleaning time is 15-30 min.

3. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (2), the mass ratio of tert-butyl hydroperoxide to glacial acetic acid is (4-6):

10.

4. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (3), the solid-liquid ratio of the pretreated fiber to the chemical catalyst solution is 5:60 to 5:80 (g / mL), the treatment temperature is 55 to 70°C, the treatment time is 4 to 8 hours, and the oscillation rate is 120 to 180 rpm.

5. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (4), the mass ratio of alkane hydroxylase AlkB, cofactor NADH, and auxiliary electron transporter ferrous ammonium sulfate is 3:(0.5-0.8):(0.1-0.2).

6. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (5), the solid-liquid ratio of the pre-activated fiber to the biocatalyst suspension is 1:40 to 2:40 (g / mL), the degradation temperature is 30 to 37°C, the degradation time is 24 to 72 h, and the oscillation rate is 100 to 150 rpm.

7. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (6), the vacuum distillation temperature is 45-55℃, and anhydrous ethanol is used for alcohol precipitation, which is allowed to stand at 4℃ for 6-12 hours.

8. The method for synergistic catalytic degradation and recycling of ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that, In step (6), the centrifugation speed is 8000-10000 rpm, the centrifugation time is 15-20 min, and the drying conditions are vacuum drying at 40-50℃ to constant weight.

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